/////////////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2018-    Equinor ASA
//  Copyright (C) 2017     Statoil ASA
//
//  ResInsight is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
//  WARRANTY; without even the implied warranty of MERCHANTABILITY or
//  FITNESS FOR A PARTICULAR PURPOSE.
//
//  See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
//  for more details.
//
/////////////////////////////////////////////////////////////////////////////////

#include "RiaColorTools.h"

#include "cvfMath.h"

#include <algorithm>
#include <cmath>

//--------------------------------------------------------------------------------------------------
/// Uses W3.org relative luminance calculation taking into account the different luminance of the different colors
/// https://www.w3.org/TR/WCAG20-TECHS/G18.html
/// Luminance is between [0, 1] so anything above 0.5 is considered in the bright half of the spectrum.
/// However, subjectively the contrast looks better if the threshold is to 0.4 so black contrast is used a bit more often.
//--------------------------------------------------------------------------------------------------
bool RiaColorTools::isBrightnessAboveThreshold(cvf::Color3f backgroundColor)
{
    if (relativeLuminance(backgroundColor) > 0.4)
    {
        return true;
    }

    return false;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
cvf::Color3f RiaColorTools::computeOffsetColor(cvf::Color3f color, float offsetFactor)
{
    float gridR = 0.0;
    float gridG = 0.0;
    float gridB = 0.0;

    if (isBrightnessAboveThreshold(color))
    {
        gridR = color.r() - (color.r() * offsetFactor);
        gridG = color.g() - (color.g() * offsetFactor);
        gridB = color.b() - (color.b() * offsetFactor);
    }
    else
    {
        gridR = color.r() + (1.0f - color.r()) * offsetFactor;
        gridG = color.g() + (1.0f - color.g()) * offsetFactor;
        gridB = color.b() + (1.0f - color.b()) * offsetFactor;
    }

    return cvf::Color3f(
        cvf::Math::clamp(gridR, 0.0f, 1.0f), cvf::Math::clamp(gridG, 0.0f, 1.0f), cvf::Math::clamp(gridB, 0.0f, 1.0f));
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
cvf::Color3f RiaColorTools::darkContrastColor()
{
    return cvf::Color3f::fromByteColor(10, 10, 10);
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
cvf::Color3f RiaColorTools::brightContrastColor()
{
    return cvf::Color3f::WHITE;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
cvf::Color3f RiaColorTools::darkContrastColorSofter()
{
    return cvf::Color3f::fromByteColor(30, 30, 30);
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
cvf::Color3f RiaColorTools::brightContrastColorSofter()
{
    return cvf::Color3f::fromByteColor(200, 200, 200);
}


//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
cvf::Color3f RiaColorTools::contrastColor(cvf::Color3f backgroundColor, bool softerContrast)
{
    if (isBrightnessAboveThreshold(backgroundColor))
    {
        if (softerContrast)
            return darkContrastColorSofter();
        return darkContrastColor();
    }
    if (softerContrast)
        return brightContrastColorSofter();
    return brightContrastColor();
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
QColor RiaColorTools::toQColor(cvf::Color3f color, float alpha)
{
    QColor qcolor(color.rByte(), color.gByte(), color.bByte());
    qcolor.setAlphaF(alpha);
    return qcolor;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
QColor RiaColorTools::toQColor(cvf::Color4f color)
{
    return toQColor(color.toColor3f(), color.a());
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
float RiaColorTools::contrastRatio(cvf::Color3f color1, cvf::Color3f color2)
{
    float L1 = relativeLuminance(color1);
    float L2 = relativeLuminance(color2);

    float Lmin = std::min(L1, L2);
    float Lmax = std::max(L1, L2);

    return (Lmax + 0.05) / (Lmin + 0.05);
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
float RiaColorTools::relativeLuminance(cvf::Color3f backgroundColor)
{
    float R = calculateNonLinearColorValue(backgroundColor.r());
    float G = calculateNonLinearColorValue(backgroundColor.g());
    float B = calculateNonLinearColorValue(backgroundColor.b());

    double luminance = 0.2126 * R + 0.7152 * G + 0.0722 * B;
    return luminance;
}

//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
float RiaColorTools::calculateNonLinearColorValue(float colorFraction)
{
    return colorFraction <= 0.03928 ? colorFraction / 12.92 : std::pow((colorFraction + 0.055) / 1.055, 2.4);
}